Client nrpe.cfg

On the client you need to specify that the server is
allowed to connect (in this case the server is 192.168.8.2)

server_port=5666
# SERVER ADDRESS
# Address that nrpe should bind to in case there are more than one interface
# and you do not want nrpe to bind on all interfaces.
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd
server_address=192.168.8.1
allowed_hosts=127.0.0.1,192.168.8.2 # Hosts allowed to talk to nrpe
nrpe_user=nagios
nrpe_group=nagios
dont_blame_nrpe=0 # If this is 1 (true), allow passing of
# arguments to commands
command_timeout=60 # kill command after this many seconds
include=/etc/nagios/nrpe_local.cfg
# So we make our changes in nrpe_local.cfg not nrpe.cfg